/* UZCARD Academy lecture hub - landing page styles.
   Visual language echoes the slide decks: white background, blue accent,
   Inter typography, generous whitespace. No framework. */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
    --bg: #ffffff;
    --bg-alt: #f5f5f7;
    --fg: #1d1d1f;
    --fg-muted: #6e6e73;
    --fg-faint: #86868b;
    --accent: #007aff;
    --accent-light: rgba(0, 122, 255, 0.08);
    --line: rgba(0, 0, 0, 0.08);
    --radius: 14px;
    --shadow: 0 1px 2px rgba(0,0,0,0.04), 0 8px 24px rgba(0,0,0,0.06);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg);
    color: var(--fg);
    line-height: 1.4;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ---------- Header ---------- */
.hub-header {
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: saturate(180%) blur(16px);
    border-bottom: 1px solid var(--line);
    z-index: 100;
}
.hub-header__inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 18px 32px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}
.hub-brand {
    display: flex;
    align-items: baseline;
    gap: 10px;
}
.hub-brand__mark {
    font-size: 18px;
    font-weight: 800;
    letter-spacing: -0.01em;
    color: var(--fg);
}
.hub-brand__sub {
    font-size: 14px;
    font-weight: 500;
    color: var(--fg-muted);
}

/* ---------- Language switcher ---------- */
.lang-switcher {
    display: inline-flex;
    background: var(--bg-alt);
    border-radius: 10px;
    padding: 3px;
    gap: 1px;
}
.lang-btn {
    background: transparent;
    border: 0;
    padding: 7px 14px;
    font-family: inherit;
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.02em;
    color: var(--fg-muted);
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 120ms ease, color 120ms ease;
}
.lang-btn:hover:not(.is-active) { color: var(--fg); }
.lang-btn.is-active {
    background: var(--bg);
    color: var(--fg);
    box-shadow: 0 1px 2px rgba(0,0,0,0.06);
}

/* ---------- Hero ---------- */
.hub-main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 56px 32px 80px;
}
.hub-hero {
    text-align: left;
    margin-bottom: 56px;
}
.hub-eyebrow {
    font-size: 13px;
    font-weight: 600;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.16em;
    margin-bottom: 12px;
}
.hub-title {
    font-size: clamp(36px, 5vw, 56px);
    font-weight: 800;
    letter-spacing: -0.025em;
    line-height: 1.05;
    margin-bottom: 14px;
}
.hub-subtitle {
    font-size: clamp(15px, 1.4vw, 18px);
    color: var(--fg-muted);
    max-width: 640px;
    line-height: 1.5;
}

/* ---------- Lecture grid ---------- */
.lecture-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 22px;
}

/* Card built by JS as an <a class="lecture-card"> */
.lecture-card {
    display: flex;
    flex-direction: column;
    padding: 26px 24px 22px;
    background: var(--bg);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    text-decoration: none;
    color: inherit;
    transition: transform 180ms ease, box-shadow 180ms ease, border-color 180ms ease;
    min-height: 180px;
    position: relative;
    overflow: hidden;
}
.lecture-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow);
    border-color: rgba(0, 122, 255, 0.3);
}
.lecture-card__number {
    font-size: 13px;
    font-weight: 700;
    color: var(--accent);
    letter-spacing: 0.16em;
    text-transform: uppercase;
    margin-bottom: 18px;
}
.lecture-card__title {
    font-size: 19px;
    font-weight: 600;
    line-height: 1.25;
    color: var(--fg);
    margin-bottom: 10px;
    flex: 1;
}
.lecture-card__kicker {
    font-size: 13px;
    color: var(--fg-faint);
    margin-top: auto;
    display: flex;
    align-items: center;
    gap: 6px;
}
.lecture-card__kicker::after {
    content: "→";
    margin-left: auto;
    font-size: 16px;
    color: var(--accent);
    opacity: 0;
    transform: translateX(-4px);
    transition: opacity 180ms ease, transform 180ms ease;
}
.lecture-card:hover .lecture-card__kicker::after {
    opacity: 1;
    transform: translateX(0);
}

/* "Coming soon" card: muted, no hover lift, no arrow. */
.lecture-card--soon {
    background: var(--bg-alt);
    border-style: dashed;
    cursor: default;
}
.lecture-card--soon:hover {
    transform: none;
    box-shadow: none;
    border-color: var(--line);
}
.lecture-card--soon .lecture-card__number {
    color: var(--fg-faint);
}
.lecture-card--soon .lecture-card__title {
    color: var(--fg-muted);
}
.lecture-card--soon .lecture-card__kicker::after {
    content: "";
}

/* ---------- Footer ---------- */
.hub-footer {
    margin-top: 80px;
    padding-top: 32px;
    border-top: 1px solid var(--line);
    font-size: 13px;
    color: var(--fg-faint);
    text-align: center;
}

@media (max-width: 640px) {
    .hub-header__inner { padding: 14px 18px; }
    .hub-main { padding: 40px 18px 64px; }
    .lecture-grid { gap: 14px; }
    .lecture-card { padding: 22px 20px 18px; min-height: 150px; }
}